Omega-3: Lifelong intakes necessary for benefits in old age?

Higher levels of omega-3 fatty acids, particularly EPA (eicosapentaenoic acid), may decrease the risk of dementia, and improve survival in older people, suggest three new studies.

Two prospective studies from Norway and France measured omega-3 levels using biomarkers and showed positive benefits for the fatty acids in relation to mortality and cognitive function, respectively.

However, supplementation of older people with high dose omega-3 does not affect mood or well-being, according to the findings of a third study from the Netherlands.

All the studies are published in the new issue of the American Journal of Clinical Nutrition.

Putting the studies into context, William Harris from Sanford Research at the University of South Dakota commented in an accompanying editorial: “In short, the story they tell is this: low in vivo concentrations of EPA and/or DHA predict an increased risk of death in frail, hospitalised octogenarians from Norway and an accelerated cognitive decline in free-living septuagenarians from France.

“On the other hand, intervention with EPA plus DHA in the healthy elderly had no effect on mental well-being.

In the Norwegian study, Morten Lindberg from the Norwegian University of Science and Technology in Trondheim and co-workers recruited 254 frail, elderly patients and measured dietary intakes of omega-3 fatty acids using plasma phospholipid concentrations of EPA.

Over the course of three years of follow-up, the researchers found that people with the lowest average plasma phospholipid EPA concentrations were about 40 per cent more likely to die, compared to people with higher levels.

Commenting on this study, Harris said: “The authors concluded that only those in the at-risk quartile might have benefited from omega-3 fatty acid supplementation. Clearly, this is a speculative extrapolation; nevertheless, it is fair to say that higher tissue omega-3 fatty acid (at least EPA) concentrations appeared to be protective.

“Although no specific mechanism of action was identified, a generalized health benefit arising from a prolonged dietary intake of oily fish (the presumed source of the plasma EPA) would surprise no one familiar with the omega-3 fatty acid literature.”

Omega-3 versus dementia

In the French study, Cecilia Samieri from Inserm (U897) in Bordeaux and co-workers followed the 1214 non-demented participants in the Three-City Study from Bordeaux. Over the course of four years, 65 of the participants developed dementia, state the researchers.

Comparing blood levels of EPA, DHA (docosahexaenoic acid), and total omega-3 levels, the researchers found that only higher blood levels of EPA were associated with a 31 per cent lower incidence of dementia.

“A high plasma EPA concentration may decrease the risk of dementia, whereas high ratios of omega-6 to omega-3 fatty acids and of AA to DHA may increase the risk of dementia, especially in depressed older persons,” stated the researchers.

“The role of EPA in dementia warrants further research,” they concluded.

Commenting on this study, Harris said: “On finding decreased concentrations of omega-3 in the impaired, one is tempted to conclude that all we need to do is increase the EPA and/or DHA intake to alter the outcome, but clearly we cannot know from a case control study whether this is true.

“Only prospective trials can address this question, and, at least to date, such trials have been less than consistent, as noted by the authors.”

Omega-3 and mood

For the Dutch study, Ondine van de Rest from Wageningen University and co-workers performed a 26-week double-blind, placebo-controlled trial with 302 volunteers. The 65-year old subjects were randomly assigned to consume high dose omega-3 (1800 mg/d EPA plus DHA), lower dose omega-3 (400 mg/d EPA plus DHA), or placebo.

While plasma concentrations of the fatty acids did increase according to the omega-3 dose, this was not associated with any significant change in the mental well-being of the volunteers in any of the groups.

“In this randomised, double-blind, placebo-controlled trial we observed no effect of EPA plus DHA supplementation for 26 wk on mental well-being in the general older population studied,” concluded van de Rest.

Commenting on this study, Harris said: “Although one can always suggest that higher doses may have been more effective, it is more likely that what is done is done; at 70 years of age, supplementation is simply unable to materially alter emotion or mentation.”

Take home message

In his summary, Harris concluded that all three studies underscored the “importance of maintaining high dietary omega-3 fatty acids intakes throughout life”.

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